Understanding the formation mechanism of galaxies at their (ghostly) extremes

Remco van der Burg & Jérémy Fensch

(email advisors)

Extremely faint and large galaxies were recently found to be surprisingly abundant in the local universe. Come and use the deepest HST images available to watch them form at high redshift!

One of the most surprising recent results in the field of galaxy formation is the discovery of a significant population of Ultra-Diffuse Galaxies (UDGs) in local galaxy clusters. These are galaxies with the size of the Milky-Way, but the mass of dwarf galaxies. Naively one would expect these apparently feeble galaxies to be easily disrupted in such a harsh dynamical environment, yet they seem to survive and stay largely intact! Theorists are currently coming up with models that can produce such galaxies in simulations; these generally invoke tidal heating scenarios arising from interactions with neighbouring galaxies. Since such a process takes time, one may expect the abundance of UDGs to increase towards the local universe. This model, along with some variations on this general scheme, have not been tested at all. We will confront the predictions of such models with observations of UDGs in the highest-redshift regime where they can still be detected. You are invited to work with ultradeep HST imaging in three photometric bands of 10 galaxy clusters around redshift 1 and compare the abundance of UDGs (if they exist at all at a mere 5 Gyr after the Big Bang) to that measured in the local Universe. This will shed light on the formation history of these elusive galaxies.

#galaxies  #observations  #HST  #highredshift  #ultradeep  #photometry

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